Method for processing image data for display using backward projection

ABSTRACT

A method for processing image data for a vehicular vision system includes providing a plurality of cameras at a vehicle so as to have respective fields of view exterior the vehicle and providing a video display screen in the vehicle. A control has a data processor for processing image data captured by the plurality of cameras. Image data captured by at least one camera of the plurality of cameras is processed at the control utilizing backward projection from individual display pixels of the two dimensional grid of display pixels of the video display screen to respective photosensing pixels of the two dimensional array of photosensing pixels of the at least one camera. Responsive to the processing of captured image data, video images derived at least in part from the processed image data are displayed.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent application Ser. No. 15/334,365, filed Oct. 26, 2016, now U.S. Pat. No. 10,187,590, which claims the filing benefits of U.S. provisional application Ser. No. 62/246,870, filed Oct. 27, 2015, which is hereby incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to a vehicle vision system for a vehicle and, more particularly, to a vehicle vision system that utilizes two or more cameras at a vehicle.

BACKGROUND OF THE INVENTION

Use of imaging sensors in vehicle imaging systems is common and known. Examples of such known systems are described in U.S. Pat. Nos. 5,949,331; 5,670,935 and/or 5,550,677, which are hereby incorporated herein by reference in their entireties.

SUMMARY OF THE INVENTION

The present invention provides a driver assistance system or vision system or imaging system for a vehicle that utilizes two or more cameras (preferably two or more CMOS cameras) to capture image data representative of images exterior of the vehicle, and provides enhanced image processing of the captured image data to provide a display of images derived from image data captured by two or more cameras, utilizing backward projection and tracing rays from the display plane (pixel) grid (backwards) to one or more source camera (pixel) grid(s) under regard of the warping and unwarping schemes of the camera and the virtual view or views which are to be generated.

The projection pixel data handling is thus reduced to just those pixels that find use on the display, which saves processing capacity (FPGA, GPU or Processor), RAM space and bus resources of the image data processing system. The system or solution of the present invention thus saves about 25 percent or more of processing power or use of the processor and FPGA processing resources and reduces the Block RAM consumption.

These and other objects, advantages, purposes and features of the present invention will become apparent upon review of the following specification in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a vehicle with a vision system that incorporates cameras in accordance with the present invention;

FIGS. 2A and 2B show image data flow of a prior art system;

FIG. 3 shows image data flow in accordance with the system of the present invention;

FIG. 4 shows a projection coordinate scheme for the system of the present invention;

FIG. 5 shows mapping of a camera pixel to a top view pixel within the output [display] pixel grid in accordance with the system of the present invention;

FIG. 6 shows the display output having a top view display and a rear view image display in combination, with the top view generated from outputs of four cameras, and with an ego vehicle and driving aids overlayed on the displayed images;

FIG. 7 is a block diagram of an image projection unit in accordance with the present invention;

FIG. 8 is an accumulator block diagram and table;

FIG. 9 is an accumulator flowchart in accordance with the present invention;

FIG. 10 is a gap flowchart and block diagram in accordance with the present invention;

FIG. 11 is a schematic showing gap filling in accordance with the present invention;

FIG. 12 is an image shown as a stretched region of video images without filled gaps; and

FIG. 13 is a view of a vehicle with one master camera and three slave cameras and a display for a surround vision system in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A vehicle vision system and/or driver assist system and/or object detection system and/or alert system operates to capture images exterior of the vehicle and may process the captured image data to display images and to detect objects at or near the vehicle and in the predicted path of the vehicle, such as to assist a driver of the vehicle in maneuvering the vehicle in a rearward direction. The vision system includes an image processor or image processing system that is operable to receive image data from one or more cameras and provide an output to a display device for displaying images representative of the captured image data. Optionally, the vision system may provide display, such as a rearview display or a top down or bird's eye or surround view display or the like.

Referring now to the drawings and the illustrative embodiments depicted therein, a vehicle 10 includes an imaging system or vision system 12 that includes at least one exterior facing imaging sensor or camera, such as a rearward facing imaging sensor or camera 14 a (and the system may optionally include multiple exterior facing imaging sensors or cameras, such as a forwardly facing camera 14 b at the front (or at the windshield) of the vehicle, and a sidewardly/rearwardly facing camera 14 c, 14 d at respective sides of the vehicle), which captures images exterior of the vehicle, with the camera having a lens for focusing images at or onto an imaging array or imaging plane or imager of the camera (FIG. 1). Optionally, a forward viewing camera may be disposed at the windshield of the vehicle and view through the windshield and forward of the vehicle, such as for a machine vision system (such as for traffic sign recognition, headlamp control, pedestrian detection, collision avoidance, lane marker detection and/or the like). The vision system 12 includes a control or electronic control unit (ECU) or processor 18 that is operable to process image data captured by the camera or cameras and may detect objects or the like and/or provide displayed images at a display device 16 for viewing by the driver of the vehicle (although shown in FIG. 1 as being part of or incorporated in or at an interior rearview mirror assembly 20 of the vehicle, the control and/or the display device may be disposed elsewhere at or in the vehicle). The data transfer or signal communication from the camera to the ECU may comprise any suitable data or communication link, such as a vehicle network bus or the like of the equipped vehicle.

The present invention provides enhanced vehicle multi-camera vision processing. Normal view and fish eye view cameras disposed at a vehicle so as to have exterior fields of view provide image data streams, which get communized in one or more altered or artificial views, such as a top down bird's eye view or the like, for being displayed to the driver of the vehicle on a display, projector or head up display or the like, or are processed by an advanced driver assistance system (ADAS) machine vision processing algorithm.

For that, the source images get unwrapped/undistorted, cropped and mathematically projected to a virtual view plane, partially alpha blended and overlayed with augmentations. The processing is done in real time, which means frame wise image capturing and displaying at a frame rate typically at 15 f/s (frames per second), 30 f/s or 60 f/s or the like. The image processing path from the cameras to one or more artificial views requires substantial amounts of processing performance in processors, FPGAs and/or GPUs as well as vehicle communication bus capacity and RAM space may these be located in the cameras, in an ECU the cameras are connected at or at a target display device with processing capabilities such as a head unit.

In special-view systems, the 2D grid or array of camera pixels does not correspond to the 2D screen pixel grid. A projection algorithm is required to transform the 2D camera grid into the 2D screen grid. Several camera inputs may be combined at a single screen.

Current solutions are based on screen-to-camera projection. The system solution according to the present invention is implemented as backward projection, tracing rays from the display plane (pixel) grid (backwards) to one or more source camera (pixel) grid(s) under regard of the warping and unwarping schemes of the camera and the virtual view or views which are to be generated. Due to that measure, the projection pixel data handling is reduced to just these pixels which really find use on the display which saves processing capacity (FPGA, GPU or Processor), RAM space and bus resources of the image data processing system.

The following description may imply a four camera architecture with the camera's imagers connected (via monodirectional or bidirectional data busses) to an ECU which bears the processing capabilities such as having one or more microprocessor cores, one or more FPGAs and RAM either integrated or extra, such as shown in FIG. 1. An alternative architecture with having the processing capabilities fully or mostly incorporate to one camera or multiple cameras will be discussed further below.

Instead of buffering all (at a surround view vision system typically four, but more are possible) camera image pixels (of one frame) in the vision system's RAM such as the FPGAs Block RAM (optionally after passing an High Dynamic Range Image Processing (HDR ISP) algorithm) for sourcing the virtual projection processing such as shown in FIG. 2A, the system may just store the source pixels (already debayered by the ISP) that are necessary for the display output image (see FIGS. 3 and 4). In the given illustrated examples, it may be assumed an 888 RGB may find use. As an alternative option, the image processing may be done in 10-8-6 RGB or 10-7-7 RGB. For that, one or more projection units may be present behind the HDR ISP for distributing the according pixels out of the incoming image data streams. A top view image is generated out of four projection planes which may have one projection unit each (see FIG. 5). Often the display is sharing another (e.g., user chosen or selected) view such as a rear view image with the top view image (see FIG. 6) which generation requires an additional projection unit. Although shown in FIG. 6 as including a rear view image and top view image, the system may also provide a forward view image and top view image to assist the driver in parking the vehicle.

Each projection unit may comprise an undistortion table, representing the camera lens parameters followed by a 3×3 vector table which is view dependent, followed by a distortion table, representing the target view distortion (see FIG. 7). Each camera sends its each column's pixels in sequence row by row (Cc=Camera column coordinate; Cr=Camera row coordinate). The (back-) projection unit addresses each pixel into an accumulator bin (Dx=Display x coordinate, Dy=Display y coordinate), see FIG. 5 (where the regions of camera pixels are projected to the same screen pixel, and all camera pixel values in the region are averaged). The system uses W accumulators and processes image data in camera scan order. A pixel value is added to the projected accumulator. If screen_y is below accu_y, the old accu is divided by the number of pixels and the average is written to SDRAM, and a new accumulation is started with the current pixels.

By that, the camera pixel content is condensed at the time of transmission of the data stream without storing whole camera images but just the display view image instead in the desired size and resolution and possibly cropped. In some image regions, multiple camera pixels of a single camera source get projected to the same display (or screen) pixel, typically those at which the density of camera pixels exceed the density of target elements (display pixels) due to distortion. Due to that, target pixels may be generated by having accumulators (W) (or bins) at which multiple source pixels get blended into one target pixel (see FIGS. 8 and 9). The blending may be done by arithmetic averaging. As an alternative slightly more complex option, the averaging may be done by arithmetic-geometric averaging or as preferred alternative option by geometric averaging in accordance to the x, y subpixel displacement. By that, the camera pixel projected closer to the target display pixel may be reflected stronger in the resulting bin value than those which are projected father away (two dimensional by that geometric).

As can be seen in FIG. 12, in some target image regions not for all display pixel (Dx, Dy) a camera source pixel is present (also due to distortion), these pixels get marked as ‘gaps’. The gaps may be stored in a list within the device memory. Optionally, the gaps may be expressed as a polygon, where the polygon corners are defined by the location of surrounding valid image elements. Due to economic reasons, the gap flags may be recorded primarily (see FIG. 10). A consecutive stage ‘gap fill’ (see FIG. 3) may be executed consecutively to the projection unit, optionally one for each unit. The gap fill stage will fill the empty target image elements or display pixel region with a blend or interpolation of the borderlining existing pixels (flagged as ‘no gap’) (see FIG. 11). Optionally, the gap fill will be done line-by-line or column-by-column of target image elements or pixels.

The blending may be done optionally by a decreasing factor depending on how far the gap pixel is away from a borderlining source pixel, done according each borderlining pixel. As an alternative option, the blending may be done by just filling the gap pixels between the borderlining pixels with the arithmetic average of all true borderlining pixels. As an alternative option, the blending may be done by filling the gap pixels by dithering duplications of all borderlining pixels, optionally under reflection of the color and brightness average and optionally by imitating the pixel noise level of that region or the whole image. By that a more noise night view image may have a more dithered noise inserted to the gap pixels than a smooth bright daylight image. The dithering may be accurate to hide the Moire pattern-like structure caused by the distortion and stretching of the camera grid as to be seen in FIG. 12.

The gap fill processing may be done in three steps: In the first step, the image processing device may calculate the two intersection points between the current line or column and the edges of the gap polygon. In the second step, the image processing device may calculate the values of each intersection point from the values of the two corner points of the crossed polygon edge. In the third step, the image processing device may calculate the values of the target image elements between the intersections from the values of the intersection points.

The target (displayed) image possesses zones at which two camera's (partial) image borderlines overlap (on purpose). These may be blended by alpha blending as the primary step before finally displaying.

As an optional alternative, the surround vision system according to the present invention may have an architecture having the processing capabilities fully or mostly incorporated to one camera or multiple cameras instead of having it on an ECU. The ECU may be spared entirely. FIG. 13 shows a vehicle 10′ having one master-camera 15 a at the vehicle's rear and three slave cameras 15 b, 15 c and 15 d at the side and at the front of the vehicle, all viewing outward or exterior or outbound from the vehicle. Optionally, the system may have just the front and the rear camera 15 a and 15 b. Optionally, side rearview mirror cameras with small opening angle to the rear or shift lens optics with high pixel density to the rear and opening to the blind spot region with reduced pixel density may be used additionally or instead of the slave cameras 15 c and 15 d. Optionally, there may be an additional rear only side camera 15 e and 15 f integrated in the side mirror region, optionally combined with 15 c and 15 d in one wing each carrying two slave cameras.

The master camera may have a monodirectional or bidirectional vision data and control line or bus to the display device 17, which may be vehicle cluster attached or integrated, head unit attached or integrated, or a head up display, projector or TFT, optionally comprising a light field display which may be visible on the bottom or top of the windshield or at a combiner or at a screen on the rearview mirror position. The slave cameras may be connected to the master camera via a bidirectional vision data and control data line or bus. All data lines may optionally also carry the supply power. The vision data may optionally be compressed via a compression codec before transmission. The used codec may be H.264, H.262, H.263, H.265, MPEG1, MPEG2, MPEG3, JPEG2000 besides others. In case compression is used, the slave cameras may run a compression algorithm before transmitting image data to the master camera. Optionally, the slave cameras send their full image data streams to the master camera which is accumulating the required display pixels in accumulator bins (in the manner as the ECU referred above) coming from its own imager and from the slave cameras. The master camera also processes the gap filling. The master camera may decompress the data before further processing. Optionally, the master camera may compress the display image before transmission to the display device 17.

In a more advanced alternative option, the slave cameras may run the projection unit and hold the accumulator bins. The slave cameras may not send the full images but just the accumulator bins content to the master camera. The master camera may carry out the accumulation of the own imagers' image data and the gap filling before sending the display image to the display 17. The system may utilize aspects of the vision systems described in U.S. Publication No. US-2014-0152778, which is hereby incorporated herein by reference in its entirety.

The camera or sensor may comprise any suitable camera or sensor. Optionally, the camera may comprise a “smart camera” that includes the imaging sensor array and associated circuitry and image processing circuitry and electrical connectors and the like as part of a camera module, such as by utilizing aspects of the vision systems described in International Publication Nos. WO 2013/081984 and/or WO 2013/081985, which are hereby incorporated herein by reference in their entireties.

The system includes an image processor operable to process image data captured by the camera or cameras, such as for detecting objects or other vehicles or pedestrians or the like in the field of view of one or more of the cameras. For example, the image processor may comprise an image processing chip selected from the EyeQ family of image processing chips available from Mobileye Vision Technologies Ltd. of Jerusalem, Israel, and may include object detection software (such as the types described in U.S. Pat. Nos. 7,855,755; 7,720,580 and/or 7,038,577, which are hereby incorporated herein by reference in their entireties), and may analyze image data to detect vehicles and/or other objects. Responsive to such image processing, and when an object or other vehicle is detected, the system may generate an alert to the driver of the vehicle and/or may generate an overlay at the displayed image to highlight or enhance display of the detected object or vehicle, in order to enhance the driver's awareness of the detected object or vehicle or hazardous condition during a driving maneuver of the equipped vehicle.

The vehicle may include any type of sensor or sensors, such as imaging sensors or radar sensors or lidar sensors or ladar sensors or ultrasonic sensors or the like. The imaging sensor or camera may capture image data for image processing and may comprise any suitable camera or sensing device, such as, for example, a two dimensional array of a plurality of photosensor elements arranged in at least 640 columns and 480 rows (at least a 640×480 imaging array, such as a megapixel imaging array or the like), with a respective lens focusing images onto respective portions of the array. The photosensor array may comprise a plurality of photosensor elements arranged in a photosensor array having rows and columns. Preferably, the imaging array has at least 300,000 photosensor elements or pixels, more preferably at least 500,000 photosensor elements or pixels and more preferably at least 1 million photosensor elements or pixels. The imaging array may capture color image data, such as via spectral filtering at the array, such as via an RGB (red, green and blue) filter or via a red/red complement filter or such as via an RCC (red, clear, clear) filter or the like. The logic and control circuit of the imaging sensor may function in any known manner, and the image processing and algorithmic processing may comprise any suitable means for processing the images and/or image data.

For example, the vision system and/or processing and/or camera and/or circuitry may utilize aspects described in U.S. Pat. Nos. 9,233,641; 9,146,898; 9,174,574; 9,090,234; 9,077,098; 8,818,042; 8,886,401; 9,077,962; 9,068,390; 9,140,789; 9,092,986; 9,205,776; 8,917,169; 8,694,224; 7,005,974; 5,760,962; 5,877,897; 5,796,094; 5,949,331; 6,222,447; 6,302,545; 6,396,397; 6,498,620; 6,523,964; 6,611,202; 6,201,642; 6,690,268; 6,717,610; 6,757,109; 6,802,617; 6,806,452; 6,822,563; 6,891,563; 6,946,978; 7,859,565; 5,550,677; 5,670,935; 6,636,258; 7,145,519; 7,161,616; 7,230,640; 7,248,283; 7,295,229; 7,301,466; 7,592,928; 7,881,496; 7,720,580; 7,038,577; 6,882,287; 5,929,786 and/or 5,786,772, which are all hereby incorporated herein by reference in their entireties. The system may communicate with other communication systems via any suitable means, such as by utilizing aspects of the systems described in International Publication Nos. WO 2010/144900; WO 2013/043661 and/or WO 2013/081985, and/or U.S. Pat. No. 9,126,525, which are hereby incorporated herein by reference in their entireties.

The imaging device and control and image processor and any associated illumination source, if applicable, may comprise any suitable components, and may utilize aspects of the cameras (such as various imaging sensors or imaging array sensors or cameras or the like, such as a CMOS imaging array sensor, a CCD sensor or other sensors or the like) and vision systems described in U.S. Pat. Nos. 5,760,962; 5,715,093; 6,922,292; 6,757,109; 6,717,610; 6,590,719; 6,201,642; 5,796,094; 6,559,435; 6,831,261; 6,822,563; 6,946,978; 7,720,580; 8,542,451; 7,965,336; 7,480,149; 5,550,677; 5,877,897; 6,498,620; 5,670,935; 5,796,094; 6,396,397; 6,806,452; 6,690,268; 7,005,974; 7,937,667; 7,123,168; 7,004,606; 6,946,978; 7,038,577; 6,353,392; 6,320,176; 6,313,454 and/or 6,824,281, and/or International Publication Nos. WO 2009/036176; WO 2009/046268; WO 2010/099416; WO 2011/028686 and/or WO 2013/016409, and/or U.S. Pat. Publication Nos. US 2010-0020170 and/or US-2009-0244361, which are all hereby incorporated herein by reference in their entireties.

The camera module and circuit chip or board and imaging sensor may be implemented and operated in connection with various vehicular vision-based systems, and/or may be operable utilizing the principles of such other vehicular systems, such as a vehicle headlamp control system, such as the type disclosed in U.S. Pat. Nos. 5,796,094; 6,097,023; 6,320,176; 6,559,435; 6,831,261; 7,004,606; 7,339,149 and/or 7,526,103, which are all hereby incorporated herein by reference in their entireties, a rain sensor, such as the types disclosed in commonly assigned U.S. Pat. Nos. 6,353,392; 6,313,454; 6,320,176 and/or 7,480,149, which are hereby incorporated herein by reference in their entireties, a vehicle vision system, such as a forwardly, sidewardly or rearwardly directed vehicle vision system utilizing principles disclosed in U.S. Pat. Nos. 5,550,677; 5,670,935; 5,760,962; 5,877,897; 5,949,331; 6,222,447; 6,302,545; 6,396,397; 6,498,620; 6,523,964; 6,611,202; 6,201,642; 6,690,268; 6,717,610; 6,757,109; 6,802,617; 6,806,452; 6,822,563; 6,891,563; 6,946,978 and/or 7,859,565, which are all hereby incorporated herein by reference in their entireties, a trailer hitching aid or tow check system, such as the type disclosed in U.S. Pat. No. 7,005,974, which is hereby incorporated herein by reference in its entirety, a reverse or sideward imaging system, such as for a lane change assistance system or lane departure warning system or for a blind spot or object detection system, such as imaging or detection systems of the types disclosed in U.S. Pat. Nos. 7,881,496; 7,720,580; 7,038,577; 5,929,786 and/or 5,786,772, which are hereby incorporated herein by reference in their entireties, a video device for internal cabin surveillance and/or video telephone function, such as disclosed in U.S. Pat. Nos. 5,760,962; 5,877,897; 6,690,268 and/or 7,370,983, and/or U.S. Publication No. US-2006-0050018, which are hereby incorporated herein by reference in their entireties, a traffic sign recognition system, a system for determining a distance to a leading or trailing vehicle or object, such as a system utilizing the principles disclosed in U.S. Pat. Nos. 6,396,397 and/or 7,123,168, which are hereby incorporated herein by reference in their entireties, and/or the like.

Optionally, the vision system may include a display for displaying images captured by one or more of the imaging sensors for viewing by the driver of the vehicle while the driver is normally operating the vehicle. Optionally, for example, the vision system may include a video display device, such as by utilizing aspects of the video display systems described in U.S. Pat. Nos. 5,530,240; 6,329,925; 7,855,755; 7,626,749; 7,581,859; 7,446,650; 7,338,177; 7,274,501; 7,255,451; 7,195,381; 7,184,190; 5,668,663; 5,724,187; 6,690,268; 7,370,983; 7,329,013; 7,308,341; 7,289,037; 7,249,860; 7,004,593; 4,546,551; 5,699,044; 4,953,305; 5,576,687; 5,632,092; 5,677,851; 5,708,410; 5,737,226; 5,802,727; 5,878,370; 6,087,953; 6,173,508; 6,222,460; 6,513,252 and/or 6,642,851, and/or U.S. Publication Nos. US-2012-0162427; US-2006-0050018 and/or US-2006-0061008, which are all hereby incorporated herein by reference in their entireties. Optionally, the video display screen or device may be operable to display images captured by a rearward viewing camera of the vehicle during a reversing maneuver of the vehicle (such as responsive to the vehicle gear actuator being placed in a reverse gear position or the like) to assist the driver in backing up the vehicle, and optionally may be operable to display the compass heading or directional heading character or icon when the vehicle is not undertaking a reversing maneuver, such as when the vehicle is being driven in a forward direction along a road (such as by utilizing aspects of the display system described in International Publication No. WO 2012/051500, which is hereby incorporated herein by reference in its entirety).

Optionally, the vision system (utilizing the forward facing camera and a rearward facing camera and other cameras disposed at the vehicle with exterior fields of view) may be part of or may provide a display of a top-down view or birds-eye view system of the vehicle or a surround view at the vehicle, such as by utilizing aspects of the vision systems described in International Publication Nos. WO 2010/099416; WO 2011/028686; WO 2012/075250; WO 2013/019795; WO 2012/075250; WO 2012/145822; WO 2013/081985; WO 2013/086249 and/or WO 2013/109869, and/or U.S. Publication No. US-2012-0162427, which are hereby incorporated herein by reference in their entireties.

Changes and modifications in the specifically described embodiments can be carried out without departing from the principles of the invention, which is intended to be limited only by the scope of the appended claims, as interpreted according to the principles of patent law including the doctrine of equivalents. 

1. A method for processing image data for a vehicular vision system, said method comprising: providing a plurality of cameras at a vehicle so as to have respective fields of view exterior the vehicle; wherein each camera of the plurality of cameras comprises a two dimensional array of photosensing pixels; wherein providing the plurality of cameras comprises (i) mounting a rear camera at a rear portion of the vehicle so as to have a field of view at least rearward of the vehicle, (ii) mounting a left-side camera at a left side portion of the vehicle so as to have a field of view at least sideward of the vehicle, (iii) mounting a right-side camera at a right side portion of the vehicle so as to have a field of view at least sideward of the vehicle and (iv) mounting a front camera at a front portion of the vehicle so as to have a field of view at least forward of the vehicle; wherein, with the plurality of cameras mounted at the vehicle, the field of view of the left-side camera partially overlaps the field of view of the front camera and partially overlaps the field of view of the rear camera, and the field of view of the right-side camera partially overlaps the field of view of the front camera and partially overlaps the field of view of the rear camera; providing a video display screen in the vehicle, wherein the video display screen comprises a two dimensional grid of display pixels; providing a control having a data processor for processing image data captured by the plurality of cameras; processing, at the control, image data captured by at least one camera of the plurality of cameras utilizing backward projection from individual display pixels of the two dimensional grid of display pixels of the video display screen to respective photosensing pixels of the two dimensional array of photosensing pixels of the at least one camera of the plurality of cameras; and responsive to the processing at the control of the image data captured by the at least one camera of the plurality of cameras, displaying, at the video display screen, video images derived at least in part from the processed image data.
 2. The method of claim 1, wherein each camera of the plurality of cameras comprises at least one million photosensing pixels.
 3. The method of claim 2, wherein processing image data captured by the at least one camera of the plurality of cameras comprises utilizing ray tracing from individual display pixels of the two dimensional grid of display pixels of the video display screen to respective photosensing pixels of the two dimensional array of photosensing pixels of the at least one camera of the plurality of cameras.
 4. The method of claim 1, wherein processing image data captured by the at least one camera of the plurality of cameras comprises restricting processing of photosensing pixels of the at least one camera of the plurality of cameras to processing of only those photosensing pixels of the at least one camera of the plurality of cameras that are used for the displayed video images.
 5. The method of claim 1, wherein processing image data captured by the at least one camera of the plurality of cameras comprises processing image data captured by all of the plurality of cameras utilizing backward projection from individual display pixels of the two dimensional grid of display pixels of the video display screen to respective photosensing pixels of the two dimensional array of photosensing pixels of each respective camera of the plurality of cameras.
 6. The method of claim 5, wherein displaying video images comprises displaying video images derived from the processed image data captured by all of the plurality of cameras to provide a surround view display.
 7. The method of claim 1, wherein processing image data captured by the at least one camera of the plurality of cameras comprises utilizing backward projection from individual display pixels of the two dimensional grid of display pixels of the video display screen to respective photosensing pixels of the two dimensional array of photosensing pixels of the one camera of the plurality of cameras.
 8. The method of claim 7, wherein displaying video images comprises displaying video images derived from the processed image data captured by the one camera of the plurality of cameras.
 9. The method of claim 1, comprising buffering data from only those photosensing pixels of the at least one camera of the plurality of cameras that are used in the backward projection.
 10. The method of claim 1, wherein processing image data captured by the at least one camera of the plurality of cameras comprises utilizing unwarping.
 11. A method for processing image data for a vehicular vision system, said method comprising: providing a plurality of cameras at a vehicle so as to have respective fields of view exterior the vehicle; wherein each camera of the plurality of cameras comprises a two dimensional array of photosensing pixels; wherein providing the plurality of cameras comprises (i) mounting a rear camera at a rear portion of the vehicle so as to have a field of view at least rearward of the vehicle, (ii) mounting a left-side camera at a left side portion of the vehicle so as to have a field of view at least sideward of the vehicle, (iii) mounting a right-side camera at a right side portion of the vehicle so as to have a field of view at least sideward of the vehicle and (iv) mounting a front camera at a front portion of the vehicle so as to have a field of view at least forward of the vehicle; wherein, with the plurality of cameras mounted at the vehicle, the field of view of the left-side camera partially overlaps the field of view of the front camera and partially overlaps the field of view of the rear camera, and the field of view of the right-side camera partially overlaps the field of view of the front camera and partially overlaps the field of view of the rear camera; providing a video display screen in the vehicle, wherein the video display screen comprises a two dimensional grid of display pixels; providing a control having a data processor for processing image data captured by the plurality of cameras; processing, at the control, image data captured by the plurality of cameras utilizing backward projection from individual display pixels of the two dimensional grid of display pixels of the video display screen to respective photosensing pixels of the two dimensional array of photosensing pixels of each respective camera of the plurality of cameras; responsive to the processing at the control of image data captured by each camera of the plurality of cameras, displaying, at the video display screen, video images derived at least in part from the processed image data to provide a surround view display; and wherein processing image data captured by each camera of the plurality of cameras comprises restricting processing of photosensing pixels of each camera of the plurality of cameras to processing of only those photosensing pixels of each camera of the plurality of cameras that are used for the displayed video images.
 12. The method of claim 11, wherein each camera of the plurality of cameras comprises at least one million photosensing pixels.
 13. The method of claim 12, wherein processing image data captured by each camera of the plurality of cameras comprises utilizing ray tracing from individual display pixels of the two dimensional grid of display pixels of the video display screen to respective photosensing pixels of the two dimensional array of photosensing pixels of each respective camera of the plurality of cameras.
 14. The method of claim 11, comprising buffering data from only those photosensing pixels of each camera of the plurality of cameras that are used in the backward projection.
 15. The method of claim 11, wherein processing image data captured by each camera of the plurality of cameras comprises utilizing unwarping.
 16. A method for processing image data for a vehicular vision system, said method comprising: providing a plurality of cameras at a vehicle so as to have respective fields of view exterior the vehicle; wherein each camera of the plurality of cameras comprises a two dimensional array of photosensing pixels; wherein providing the plurality of cameras comprises (i) mounting a rear camera at a rear portion of the vehicle so as to have a field of view at least rearward of the vehicle, (ii) mounting a left-side camera at a left side portion of the vehicle so as to have a field of view at least sideward of the vehicle, (iii) mounting a right-side camera at a right side portion of the vehicle so as to have a field of view at least sideward of the vehicle and (iv) mounting a front camera at a front portion of the vehicle so as to have a field of view at least forward of the vehicle; wherein, with the plurality of cameras mounted at the vehicle, the field of view of the left-side camera partially overlaps the field of view of the front camera and partially overlaps the field of view of the rear camera, and the field of view of the right-side camera partially overlaps the field of view of the front camera and partially overlaps the field of view of the rear camera; providing a video display screen in the vehicle, wherein the video display screen comprises a two dimensional grid of display pixels; providing a control having a data processor for processing image data captured by the plurality of cameras; processing, at the control, image data captured by one camera of the plurality of cameras utilizing backward projection from individual display pixels of the two dimensional grid of display pixels of the video display screen to respective photosensing pixels of the two dimensional array of photosensing pixels of the one camera of the plurality of cameras; responsive to the processing at the control of the image data captured by the one camera of the plurality of cameras, displaying, at the video display screen, video images derived at least in part from the processed image data; and wherein processing image data captured by the one camera of the plurality of cameras comprises restricting processing of photosensing pixels of the one camera of the plurality of cameras to processing of only those photosensing pixels of the one camera of the plurality of cameras that are used for the displayed video images.
 17. The method of claim 16, wherein each camera of the plurality of cameras comprises at least one million photosensing pixels.
 18. The method of claim 17, wherein processing image data captured by the one camera of the plurality of cameras comprises utilizing ray tracing from individual display pixels of the two dimensional grid of display pixels of the video display screen to respective photosensing pixels of the two dimensional array of photosensing pixels of the one camera of the plurality of cameras.
 19. The method of claim 16, comprising buffering data from only those photosensing pixels of the one camera of the plurality of cameras that are used in the backward projection.
 20. The method of claim 16, wherein processing image data captured by the one camera of the plurality of cameras comprises utilizing unwarping. 